/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    Item.java
 *    Copyright (C) 2010-2012 University of Waikato, Hamilton, New Zealand
 *
 */
package weka.associations;

import java.io.Serializable;

import weka.core.Attribute;

/**
 * Class that encapsulates information about an individual item. An item is a
 * value of a nominal attribute, so this class has a backing Attribute.
 * 
 * @author Mark Hall (mhall{[at]}pentaho{[dot]}com).
 * @version $Revision$
 */
public abstract class Item implements Serializable, Comparable<Item> {

    /** For serialization */
    private static final long serialVersionUID = -430198211081183575L;

    /** The frequency of this item */
    protected int m_frequency;

    /** The attribute that backs this item */
    protected Attribute m_attribute;

    public Item(Attribute att) {
        m_attribute = att;
    }

    /**
     * Increase the frequency of this item.
     * 
     * @param f the amount to increase the frequency by.
     */
    public void increaseFrequency(int f) {
        m_frequency += f;
    }

    /**
     * Decrease the frequency of this item.
     * 
     * @param f the amount by which to decrease the frequency.
     */
    public void decreaseFrequency(int f) {
        m_frequency -= f;
    }

    /**
     * Increment the frequency of this item.
     */
    public void increaseFrequency() {
        m_frequency++;
    }

    /**
     * Decrement the frequency of this item.
     */
    public void decreaseFrequency() {
        m_frequency--;
    }

    /**
     * Get the frequency of this item.
     * 
     * @return the frequency.
     */
    public int getFrequency() {
        return m_frequency;
    }

    /**
     * Get the attribute that this item originates from.
     * 
     * @return the corresponding attribute.
     */
    public Attribute getAttribute() {
        return m_attribute;
    }

    /**
     * Get this item's value as a String.
     * 
     * @return this item's value as a String.
     */
    public abstract String getItemValueAsString();

    /**
     * Get this item's comparison operator as a String.
     * 
     * @return this item's comparison operator as a String.
     */
    public abstract String getComparisonAsString();

    /**
     * A string representation of this item. (i.e. <attribute name> <comparison
     * operator> <item value>).
     * 
     * @return a string representation of this item.
     */
    public String toString() {
        return toString(false);
    }

    /**
     * A string representation of this item, (i.e. <attribute name> <comparison
     * operator> <item value>). This default implementation just prints the
     * attribute name and (optionally) frequency information.
     * 
     * @param freq true if the frequency should be included.
     * @return a string representation of this item.
     */
    public String toString(boolean freq) {
        String result = m_attribute.name();
        if (freq) {
            result += ":" + m_frequency;
        }
        return result;
    }

    /**
     * Ensures that items will be sorted in descending order of frequency. Ties are
     * ordered by attribute name.
     * 
     * @param comp the Item to compare against.
     */
    public int compareTo(Item comp) {
        if (m_frequency == comp.getFrequency()) {
            // sort by name
            return -1 * m_attribute.name().compareTo(comp.getAttribute().name());
        }
        if (comp.getFrequency() < m_frequency) {
            return -1;
        }
        return 1;
    }

    /**
     * Equals. Just compares attribute.
     * 
     * @return true if this Item is equal to the argument.
     */
    public boolean equals(Object compareTo) {
        if (!(compareTo instanceof Item)) {
            return false;
        }

        Item b = (Item) compareTo;
        if (m_attribute.equals(b.getAttribute())) {
            return true;
        }

        return false;
    }

    public int hashCode() {
        return (m_attribute.name().hashCode() ^ m_attribute.numValues()) * m_frequency;
    }
}